In a piezoelectric component (SAW device) equipped on a mobile phone, it is necessary to ensure a space, within which electrodes are oscillated due to a piezoelectric effect, and a predetermined hollow section around their comb electrode sections (IDT electrodes) is essential.
Conventionally, in order reduce the size of a SAW device, a SAW device chip is flip-chip bonded (face-down bonded) on a wiring substrate with use of a gold (Au) bump or solder bump, and the entirety of the SAW device chip is sealed with a resin or the like, to thereby configure a small size package device of a SAW device.
Furthermore, there has been proposed a microminiaturized chip-size package SAW device in which, in order to reduce the size and height of a SAW device, a predetermined hollow section is formed around comb electrode sections, the entirety of an aggregate piezoelectric substrate (wafer) on the comb electrodes side is sealed with a resin while retaining this hollow section, and having formed external connection electrodes, it is divided, by means of dicing, into individual SAW devices.
For example, in the SAW device disclosed in Patent Document 1 (Japanese Unexamined Patent Publication No. 2006-108993), a clearance (hollow section) formation layer (outer periphery wall) composed of a photosensitive resin is formed on the upper surface of a SAW chip (piezoelectric substrate), on which comb electrodes are formed, and a sealing layer (ceiling section) is laminated and sealed on this clearance formation layer, to thereby form a clearance (hollow section) around the comb electrodes.
Moreover, in the SAW device disclosed in Patent Document 2 (Japanese Unexamined Patent Publication No. 2006-197554), a cover having through electrodes is joined and sealed via a metallic joint section so as to face the SAW chip (piezoelectric substrate) having comb electrodes formed thereon, and a hollow section is formed between the SAW chip and the cover to accommodate the comb electrodes.
Moreover, in the SAW device disclosed in Patent Document 3 (Japanese Unexamined Patent Publication No. 2007-142770), a SAW element is provided on the surface of a piezoelectric substrate, a first resin section having a hollow section is provided on this SAW element, and a second resin section is provided on this first resin section, and a silica filler is added to this second resin section, to improve the elastic modulus of the second resin section (ceiling section).